It's terrible what Omni Group did to OmniOutliner. It was such a good product - then the "upgrade" removed one of its most valuable features: the Note Pane. The only way to get it back is to upgrade further, to the costliest version.

The Note Pane is just a field where you can enter text for any outline item. What a concept. But this should be reserved for their most expensive version, due to customer research, they told me. Feh.